The following disclosure relates generally to aircraft engine nacelles and, more particularly, to apparatuses and methods for attaching engine nacelles to aircraft wings.
Propulsion systems for jet aircraft typically include at least one engine housed in an engine nacelle, an inlet positioned forward of the engine nacelle to provide air to the engine, and an outlet positioned aft of the engine nacelle to discharge exhaust gas from the engine. The engine nacelles of these systems can be placed in a number of different positions on different aircraft. For example, some transport aircraft have engine nacelles positioned below the main wing or adjacent to an aft portion of the fuselage. Some military aircraft have twin engine nacelles positioned side by side at the aft end of the fuselage. Often, such military aircraft include flight control surfaces (e.g., rudders and/or elevators) extending outwardly from the engine nacelles.
Regardless of where an engine nacelle is attached to a particular aircraft, the supporting structure must be sufficient to carry the significant loads that are often associated with engine nacelles. These loads can include engine thrust loads as well as inertial loads resulting from the weight of the engine and the nacelle structure. In addition, these loads can include torsional loads resulting from flight control surfaces extending from the nacelle, as well as torsional loads resulting from a potential engine rotor seizure.
Because of the significant loads associated with engine nacelles, engine nacelles are typically attached to engines or pylons. Engines and pylons are typically attached to major structural portions of the airframe, such as the wing-box or the fuselage. Structural portions such as these typically have enough cross-sectional depth to efficiently carry the high torsional loads often associated with engine nacelles. By xe2x80x9cefficientlyxe2x80x9d it is meant that these structural portions can carry the high torsional loads without requiring a significant amount of structural reinforcement to prevent excessive deflection or structural failure.
For performance and other reasons, however, it may be desirable to attach an engine nacelle adjacent to a relatively thin portion of an airframe, such as an aft deck region of a wing. In this situation, the thin portion typically requires a significant amount of structural reinforcement to prevent excessive deflection or structural failure under the high nacelle loads. This reinforcement can add a significant amount of weight to the airframe and adversely affect performance, as measured by fuel efficiency, passenger capacity, maneuverability, and weight and balance.
Aspects of the invention are directed to aircraft engine nacelles and methods for structurally attaching them to aircraft. In one aspect, an engine nacelle for use with an aircraft includes an interior portion, a forward portion, and a side portion. The interior portion can be configured to house an engine at least generally aligned with a central axis. The forward portion can be configured to fixedly attach the engine nacelle to the wing and transfer torsional loads from the engine nacelle into the wing. These torsional loads can include torsional loads acting at least generally parallel to the central axis. The side portion can be configured to fixedly attach the engine nacelle to the wing at least generally aft of the trailing edge region and transfer vertical and lateral loads into the wing. These vertical and lateral loads can include loads acting at least generally perpendicular to the central axis.
In another aspect of the invention, the aircraft can include a wing having a trailing edge region and an aft deck region. The aft deck region can extend aft of the trailing edge region and inboard of the trailing edge region. The forward portion of the engine nacelle can be configured to be attached at least proximate to the trailing edge region, and the side portion of the engine nacelle can be configured to be attached at least proximate to the aft deck region.
In a further aspect of the invention, a method for structurally attaching an engine nacelle to an aircraft having a wing with a trailing edge region includes providing a forward nacelle portion having first and second structural attach points. In this aspect of the invention, the engine nacelle can include an interior portion configured to house an engine at least generally aligned with a central axis, and the first and second structural attach points being offset from each other in a first direction at least generally perpendicular to the central axis. The method can further include providing a side nacelle portion positioned aft of the forward nacelle portion and having at least a third structural attach point. The third structural attach point can be offset from the first and second structural attach points in a second direction at least generally parallel to the central axis. The method can also include attaching the first and second structural attach points to the wing to transfer torsional loads from the engine nacelle into the wing, and attaching the third structural attach point to the aircraft aft of the trailing edge region of the wing to transfer at least vertical and lateral loads from the engine nacelle into the aircraft. In a further aspect of the invention, the wing can include a wing spar, and attaching the first and second structural attach points to the wing can include fixedly attaching the first and second structural attach points at least proximate to the wing spar.